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For a small project I'm working on, I am trying to decide the best route to take for the power connection to the device. It will be running on 5V and, in its current iteration, draws less than 100mA so it would be viable to power it off of USB.

The project will be a kit that needs to be assembled so I need to stick with through-hole parts that could be soldered by a relative novice. The usual go-to power connector for these projects seems to be the 2.1mm barrel connector but I really don't like those for a lot of reasons. Partly because it takes up a lot of board space (and my board will have little to spare) but mainly because that means I would also have to provide barrel connector wall adapters with the kit. This adds extra cost and parts I have to handle.

A microUSB connection would be fantastic since almost everyone has at least a few of those cables around and you could power it from a wall adapter or directly from a computer. However, I have yet to find any microUSB female sockets that are in any way easy to solder.

I've found things like this USB to 2.1mm barrel cable, but that seems like a cop-out.

Any other options that I'm missing?

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  • \$\begingroup\$ how about just a header with a few pins, you could make it reversible with 3 or 4 pins. "p n p" or "p n n p" \$\endgroup\$ – Grady Player Mar 14 '13 at 2:30
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Micro-usb tends to be SMT only. And since you think 2.1mm sockets are too bulky, usb B (and non-standard A) are out of the question. So go with the next standard. Mini-USB. Same pcb area usage as micro-usb, and still very popular and in current use as it's only just being phased out of devices.

This molex part 0548190519 for example, is a Through Hole Mini-USB B connector. They also have a mini-usb AB, otherwise known as usb-otg connector. The pins are packed together, but nothing that anyone who's ever tried soic or sot devices couldn't handle. It's a cinch.

Alternatively, you could solder on the smd mini or micro usb connector, and leave the rest to the people who buy the kit.

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Soldering surface mount USB sockets is not that bad, the solder will wick to the pins so you don't have to worry too much about accuracy as long as you don't use too much solder. With plenty of flux and a fine/mini hoof tip you should have no problem. It depends on how easy you want to make the kit, but most folk should be able to manage soldering a mini USB at least.
So I think I'd go for the USB connector, but maybe a micro one and try and find a package with the pins sticking out a bit so it's easier to get the iron to (I have had to snap the little metal tab off a couple I have used, to make it easier to access the pins)

Also, you can extend the pads further out than normal to make it easy for the solder to wick up the pads to the pins. So e.g. make the pads in the footprint below (from this datasheet) something like 2.5mm long instead of the 1.35mm shown.

USB Footprint

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  • \$\begingroup\$ @Chris - the footprint shown is for a micro USB (this one) I agree about the shield - that's what I am referring with the mention of the tab, it's quite easy to break off with pliers as you say (and/or making the pads longer helps) \$\endgroup\$ – Oli Glaser Mar 14 '13 at 3:16
  • \$\begingroup\$ Yeah, my main concern is ease of assembly. The idea is for this to be pretty much on the beginner side, difficulty wise. So an SMD part would be a bit more than beginner. If I had the manufacturing capability, I would just solder that one part on at the "factory" and ship the rest unassembled. \$\endgroup\$ – Adam Haile Mar 14 '13 at 3:22
  • \$\begingroup\$ @AdamHaile - I understand your concern, I had the same issue with a through hole guitar tuner kit a while back (trying to keep it all through hole but make it small) I think the trouble is not the actual difficulty of soldering SMT components, it's the perceived difficulty by many hobbyists out there. I actually find many SMT components easier/quicker to solder than through hole, but it's convincing your customers it's not so difficult I guess is the issue. You are a bit limited for small connectors with through hole, so maybe the barrel connector... \$\endgroup\$ – Oli Glaser Mar 14 '13 at 3:29
  • \$\begingroup\$ or similar (try Mouser, they have a massive range - you may find a nice "mini version", we just used a couple of smallish barrel connectors from them on some effects pedals) is the way to go. \$\endgroup\$ – Oli Glaser Mar 14 '13 at 3:29
  • \$\begingroup\$ Agreed... you could probably do a lot worse for first time then SMT then a micro connector. At least they usually have the larger tabs you can solder first and then do the pads. \$\endgroup\$ – Adam Haile Mar 14 '13 at 3:30

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